Influence of nanoscale structural heterogeneity on shear banding in metallic glasses
Influence of nanoscale structural heterogeneity on shear banding in metallic glasses
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DOI：
10.1016/j.actamat.2017.05.057
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发表时间：
2017-08
期刊：
影响因子：
9.4
通讯作者：
P. Zhao;Ju Li;Jinwoo Hwang;Yunzhi Wang
中科院分区：
文献类型：
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作者：
P. Zhao;Ju Li;Jinwoo Hwang;Yunzhi Wang
纳米尺度的结构异质性，例如金属玻璃（MG）中的中程有序（MRO），多年来一直被理论和模拟所暗示，最近又通过实验观察到。然而，它与塑性变形的相关性仍然知之甚少，并且对这种相关性的研究才刚刚开始。在本研究中，我们首先提出了剪切转变区（STZ）的特性与 MRO 长度尺度上的局部结构信息之间的相关性。实验表明，MRO 在 MG 中表现出不同类型的原子顺序和对称性，这在很大程度上取决于加工历史和使用条件。然后，我们进行 STZ 动力学模拟，以记录不同 STZ 的体积分数和对称性（源自 MRO 的实验表征）对剪切带动力学和应力应变行为的影响。特别是，观察到“沉淀硬化”效应并引入“应变挫败”来解释和更好地理解纳米级结构异质性对 MG 机械行为的影响。我们的方法旨在为 MG 的机械性能与其 MRO 级结构异质性之间的关系提供新的基本见解。
Structural heterogeneity at the nanoscale such as medium-range order (MRO) in metallic glasses (MGs) has been suggested by theories and simulations for many years and recently been observed by experiments. However, its correlation with plastic deformation is still poorly understood and investigation into this correlation has just begun. In this study, we first propose a correlation between the properties of shear transformation zone (STZ) and the local structural information at the MRO length scale. As revealed by experiments, the MRO exhibits different types of atomic order and symmetry in MGs depending strongly on the processing history and service condition. We then carry out STZ dynamics simulations to document effects of volume fraction and symmetry of dissimilar STZs (derived from experimental characterization of the MRO) on shear banding dynamics and stress-strain behavior. In particular, a “precipitation-hardening” effect is observed and “strain frustration” is introduced to explain and better understand the influence of nanoscale structural heterogeneity on mechanical behavior of MGs. Our approach intends to provide new fundamental insights into the relationship between the mechanical properties of MGs and their MRO-level structural heterogeneities.